Before a drug can be marketed or sold in a given country, the drug must be approved by the country's ministry of health or similar regulatory body (for example, the United States Federal Drug Administration). In order to gain such approval, pharmaceutical companies sponsor a number of clinical trial studies that are designed to determine the efficacy and safety of the drug. Pharmaceutical companies often make decisions about which clinical trial studies to sponsor based on cost estimates of the clinical trial studies. Implementing a clinical trial study can be quite complex and costs can be difficult to estimate, especially if the costs are determined using an inaccurate model of the clinical trial study.